They said some of the children treated in this manner currently show no signs of infection, though they declined to provide specifics. Preliminary data will be presented at a scientific conference in May.
"Some of the early treated children exhibited sustained virologic suppression, meaning that their HIV viral load continues to be undetectable," said microbiologist Hugo Soudeyns from Ste-Justine Hospital in Montreal.
Soudeyns is one of the investigators in a recently funded study which aims to see if starting at-risk infants on treatment-dose AIDS medications in the first 72 hours of life leads to better outcomes than starting the drugs after HIV infection has been confirmed.
There has been growing excitement about this approach since U.S. doctors announced last year that they may have cured a baby of HIV by beginning aggressive drug treatment within two days of birth. The so-called Mississippi baby is now 3 1/2 years old and appears to be virus-free, two years after being taken off AIDS drugs.
Earlier this week another U.S. team reported what appears to be a second success, in a baby from California. That girl, now nine months old, is still being given AIDS medication. There was talk at that conference, in Boston, that a number of children from Canada might also have been successfully treated in the same manner.
On Friday, a team of Canadian researchers confirmed there have been at least five, and they are looking to see if there have been more.
The scientists — from St. Justine Hospital, the Children's Hospital of Eastern Ontario in Ottawa and the Hospital for Sick Children in Toronto — have received nearly $2 million in funding from the Canadian Institutes of Health Research, the International AIDS Society and the Canadian Foundation for AIDS Research to look into what can be learned from studying the early treatment children.
Dr. Lindy Samson of the Children's Hospital of Eastern Ontario said it has been the practice in Canada for the past five or 10 years to begin early treatment of babies born to HIV-positive women when the mother's infection was not well controlled by drugs.
But Samson, who is also part of the research team, cautioned it is too soon to use the word cure in relation to this approach.
"We are very focused on trying to understand whether early treatment in infants living with HIV infection may lead to an ability or an enhanced ability to control the virus," she said.
"However ... we do not want to raise unrealistic expectations amongst the patients and their parents regarding any talk of cure, which is premature at this point in time."
Soudeyns said it even remains to be seen if the so-called "Mississippi baby" is actually cured. "The jury is still out."
A leading Canadian AIDS researcher, who has a peripheral role in the study, is even more cautious in his assessment of this treatment approach.
Dr. Mark Wainberg of McGill University in Montreal said most infants born to HIV-positive mothers are not infected with the virus, even when the mother's infection isn't controlled by AIDS medication. In the era before AIDS drugs were available, only one in four children born to infected women went on to be HIV positive, he said.
Wainberg questions whether anyone can be sure that the babies treated with this regimen were actually HIV positive. Wainberg said the infants could have had some circulating virus at birth, but may not have been truly infected.
"They may be claiming cure when in fact the infection was never really rooted in the classical way," he said, adding that it might be difficult to prove or disprove whether this treatment approach worked.
Soudeyns insisted the Canadian researchers are satisfied that the children they are studying were infected.
"The children evaluated so far were diagnosed as HIV-infected using strict clinical and laboratory testing," he said. "The clinicians on our team are confident that the children were properly diagnosed."
Meanwhile, another Canadian expert said extolling the possible success of this protocol ignores the fact that a treatment regimen for infected infants shouldn't be needed.
Dr. Julio Montaner, director of the B.C. Centre for Excellence in HIV-AIDS, said that if a mother-to-be's infection is well managed with medication, she won't transmit the virus to her child.
"Today any (pediatric) case of HIV ... should be considered a serious breakdown of our public health strategy," Montaner said.
"I find it problematic that we're focusing on the success story that the treatment of the kid represents without putting it in the proper perspective — that this shouldn't happen to begin with."
He said in British Columbia over the past decade, there have been 300 babies born to women with HIV. Two of those babies were born HIV positive.
"This as a Plan B for those two children is something that we celebrate," Montaner said. "But we need to recognize that if we had a proactive, progressive, liberal strategy to make testing widely available and treatment similarly widely available, then none of this would happen."